Spark gap with disposable solid dielectric between the electrodes



Jan. 16, 1968 SPARK GAP WITH DISPOSABLE] SOLID DIELECTRIC D1 SCHA {26E VOLTAGE sou RCE A. KARP ET AL 3,364,390

BETWEEN THE ELECTRODES Filed April 12, 1966 /V\ OTOR RELAY I 50 MOTOR CURRENT SOURCE INVENTORS ARTHUR /(A RP w/u/AM L. com/1. M S

United States Patent Office 3,364,390 Patented Jan. 16, 1968 3,364,390 SEARK GAP WHTH DTSPOSABLE SOLE) DH- ELECTREC BETWEEN THE ELECTRODES Arthur Karp, Los Altos, and William L. (Iornelius, Mountain View, (Calif., assignors to Stanford Research institute, Menlo Park, Califi, a corporation of California Filed Apr. 12, 1966, Ser. No. 542,117 4 (Claims. (Cl. 315-626) This invention relates to spark gaps and more particularly to an improved dielectric therefor.

Spark gaps are finding use nowadays in apparatus such as protection devices, voltage limiters, ultrafast switches, and as sources of short pulses of light and radio waves. It is desirable to immerse the spark gap in a dielectric since this enables a higher voltage operation with a given speed of action, or enables a shorter gap and higher speed for a given voltage, with less erosion of the points.

Pressurized, noncorrosive gases are often used as the dielectric, though there are disadvantages and hazards attendant thereto. Liquids (dielectric oils) are sometimes used, but the oil quickly becomes contaminated with products of decomposition due to the spark. Usually a pump is used to keep circulating freshly filtered or distilled oil, but problems arise since there may be bubbles in the liquid. In practice, it is also impossible to properly circulate and clean the oil fast enough.

An object of this invention is the provision of a novel dielectric for a spark gap.

Yet another object of this invention is the provision of a novel replaceable dielectric for a spark gap.

Still another object of the present invention is the provision of a simple, safe and inexpensive arrangement for replacing the dielectric in a spark gap.

These and other objects of the invention are achieved by providing a solid dielectric in the form of a tape which is moved between the points of the spark gap for use and thereafter is replaced by a fresh strip of dielectric tape.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic representation of an embodiment of the invention; and

FIGURE 2 is a detail of FIGURE 1.

The schematic embodiment of the invention shown in FIGURE 1 illustrates a discharge voltage source which provides a voltage required for enabling a discharge to occur between the two spark gap electrodes 12, 14. By way of illustration, a switch 16 represents any of the arrangements used, which when operated, cause an application of a sufficient voltage by the discharge voltage source 10 across the electrodes 12, 14 whereby a spark discharge will occur in the space between the ends of the two electrodes.

There is placed between the two electrodes, in accordance with this invention, a solid dielectric tape 18 which is fed from a pay-01f reel 20, between the two electrodes, to a take-up reel 22. The take-up reel 22 is actuated by a motor 24. Whenever the switch 16 is operated, a signal is sent to operate a relay 2d which closes its relay contacts 28. A motor current source 30 is thereby enabled to apply current to the motor 24 for as long as the relay contacts 28 remain closed. The motor turns the take-up reel 22 to pull a fresh piece of dielectric tape between the spark electrodes 12, 14.

The operation of the switch 16 is momentary so that the relay 26 remains closed only long enough to enable the motor to actuate the take-up reel to pull a fresh piece of dielectric tape into position between the spark gap electrodes. It should be noted that the arrangement for advancing the .solid dielectric through the spark gap is exemplary and is not to be constructed as a limitation upon the invention. The solid dielectric may be pulled through manually, or the mechanism for pulling it through may be actuated by other suitable arrangements, such as any means for sensing the currents of the spark discharge which actuates proper equipment to accomplish the ad vancement of the solid dielectric.

FIGURE 2 is an enlarged detail of the ends of the spark electrodes 12, 14 and the dielectric tape 18 showing the width dimension of the tape relative to the spark gap electrode dimension. This width should be wide enough so that when the spark gap fires, break down occurs through the tape thickness rather than around its surface. The solid dielectric tape 18 may be a plastic dielectric material, such as Mylar or Teflon. Alternatively, it may be a spongy paper impregnated with a liquid dielectric.

There has accordingly been described and shown herein a novel, useful arrangement for providing a solid dielectric for a spark gap, which is replaceable, whereby the advantages of using a dielectric material, other than air, are achieved for the spark gap device.

What is claimed is:

l. A spark gap arrangement comprising two spaced electrodes, a ribbon of a solid dielectric material a portion of which is positioned in the space between said two spaced electrodes, means for applying a potential to said spaced electrodes to cause a spark discharge to occur therebetween, means for moving said ribbon of said solid dielectric material and means for simultaneously actuating said potential-applying means and said ribbonmoving means to ensure the maintainance of a dielectric between said spaced electrodes.

2. Apparatus as recited in claim 1 wherein said tape width exceeds the dimensions of the ends of said spaced electrodes by an amount sufiicient to insure that dielectric breakdown occurs through the thickness of said tape rather than through its surface.

3. Apparatus as recited in claim 1 wherein said solid dielectric comprises a plastic dielectric tape.

4. Apparatus as recited in claim 1 wherein said solid dielectric comprises a tape made of spongy material impregnated with a liquid dielectric material.

References Cited UNITED STATES PATENTS 426,082 4/1890 Thomson 313-325 X 1,805,195 5/1931 Tanberg 313-325 X 2,678,373 5/1954 Suran 219-384 2,763,759 9/1956 Mito et a1 219-384 JAMES W. LAWRENCE, Primary Examiner. C. R. CAMPBELL, Assistant Examiner. 

1. A SPARK GAP ARRANGEMENT COMPRISING TWO SPACED ELECTRODES, A RIBBON OF A SOLID DIELECTRIC MATERIAL A PORTION OF WHICH IS POSITIONED IN THE SPACE BETWEEN SAID TWO SPACED ELECTRODES, MEANS FOR APPLYING A POTENTIAL TO SAID SPACED ELECTRODES TO CAUSE A SPARK DISCHARGE TO OCCUR THEREBETWEEN, MEANS FOR MOVING SAID RIBBON OF SAID SOLID DIELECTRIC MATERIAL AND MEANS FOR SIMULTANEOUSLY ACTUATING SAID POTENTIAL-APPLYING MEANS AND SAID RIBBONMOVING MEANS TO ENSURE THE MAINTAINANCE OF A DIELECTRIC BETWEEN SAID SPACED ELECTRODES. 